How can fulsome constitute "a case of ironic understatement"?
Pretend that you're Devil's Advocate. 1. How can you possibly contend that fulsome is "a case of ironic understatement"?
What's fulsome understating?
"fulsome" feels redundant for 2 reasons.
If something's FULL (e.g. a cup of water), then it's physically impossible to add anything (let alone -SOM "to a considerable degree" — or something) to it.
Fullness implies the notion of "to a considerable degree". If you own a full tank of petrol, then you have petrol to a considerate degree!
mid-13c., "abundant, plentiful," Middle English compound of ful "full" (see full (adj.)) + -som "to a considerable degree" (see -some (1)). Perhaps a case of ironic understatement. Sense extended to "plump, well-fed" (mid-14c.), then "arousing disgust" (similar to the feeling of having over-eaten), late 14c. Via the sense of "causing nausea" it came to be used of language, "offensive to taste or good manners" (early 15c.); especially "excessively flattering" (1660s). Since the 1960s, however, it commonly has been used in its original, favorable sense, especially in fulsome praise.